1. Field of the Invention
The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having a magnetic recording thin film and also to a method of and an apparatus for manufacturing it.
2. Description of the Prior Art
Magnetic recording media are widely used in the field of audio visual systems and the field of information processing systems. Recently, with the rapid progress of technologies in these fields, the recording media are required to be higher in recording density, higher in reliability and lower in cost.
Conventionally, a wide variety of magnetic materials are used in diversified forms such as tapes, discs, cards, etc., in which thin film made of magnetic iron oxide powder is mainly made available for constituting magnetic recording medium having significantly improved recording density. Nevertheless, since such thin film is not continuously formed but merely by dispersing iron oxide in resin, it is relatively low in recording density and the signal quality (i.e., signal to noise (S/N) ratio). To compensate for this, metallic film made of compound of cobalt, iron, and chrome is widely used for metallic video tapes or sputter type hard discs. On the other hand, although metallic thin film medium used for recording medium has better magnetic characteristic than that of oxidized materials, due to influence of atmospheric moisture and oxygen, it is gradually degraded via corrosion. As a result, in order to practically apply metallic film medium, manufacturer needs to improve resistivity of the film medium against corrosion by providing the film surface with coating of layers composed of organic materials or non-magnetic oxide like the one typically proposed by those prior arts including Japanese Patents Laid-Open Nos. 58-189827 (1983) and 62-293509 (1987) for example. Nevertheless, coating of those materials cited above disadvantageously results in the increased production stages and cost.
On the other hand, it is reported in those prior arts including Japanese Patents Laid-Open Nos. 60-25012 (1985) and 62-297437 (1987) for example that iron nitride and iron carbide are not only chemically stable, but both materials also proved to be comparable in magnetic characteristics to that of metallic material. Iron nitride and iron carbide are soft magnetic materials, having high saturation magnetization, and thus, those who are concerned positively follow up studies for effectively applying these to the production of head material.
Nevertheless, studies on the application of ferrous compounds to the magnetic recording medium are not yet fully expedited except for study on iron oxide such as iron carbide and iron nitride mentioned above, and yet, no preceding art has ever reported the development of iron carbide having capability of retaining sufficient magnetic force durable enough for practical application to recording medium.
Conventionally, in addition to plating process, "physical vapor deposition process" (hereinafter called PVD process) such as sputter process and vacuum evaporation process, etc. is mainly used for the production of magnetic compound thin film. Nevertheless, compared to "chemical vapor deposition process" (hereinafter called CVD process), since the energy of particles emitted from the mother material is low in the PVD process, the PVD process is not suited for the production of magnetic compound thin film.
Replacing the PVD process, manufacturers recently plan to manufacture magnetic compound thin film featuring satisfactory crystalline characteristic in presence of low temperature by applying "electron cyclotron resonance plasma enhanced chemical vapor deposition" process (hereinafter called ECR-CVD process) using radio wave plasma. This art is disclosed by Japanese Patent Laid-Open No. 60-110112 (1984) and publicized in the publication of Physical Society of Japan, Vol. 22, L210, 1983, by Matsuo and Kikuchi.